Application of the reversible / resistant model to explosives sorption in natural soils

Allen, HerbertDi Toro, Dominic M.The objective of this research is to quantify the reversibility and resistance of explosives sorption onto natural soils by the application of a predictive model that has had prior success in modeling the behavior of other organic compounds. The reversibility of sorption and resistance to desorption was investigated using HMX, RDX, Nitroglycerin (NG), TNT, and 2,4-DNT sorbed onto four soils that vary in their physical and chemical properties. After every sorption, four consecutive desorptions were initiated and the fraction of sorbate resistant to desorption was estimated after extrapolation to an infinite number of desorptions. Partition coefficients for the nitroaromatic compounds (NACs), including TNT and 2,4-DNT were largest, ranging from 3.6-46.6 L/kg. Partition coefficients for HMX ranged from 1.0-16.7 L/kg, and for NG ranged from 0.2-13.1 L/kg. RDX was the least strongly sorbed, with partition coefficients ranging from 0.3-6.9 L/kg. Sorption of HMX, RDX, and NG appears to be controlled by the organic matter (OM) content of the soil, but TNT and 2,4-DNT will sorb strongly to soils with nominal organic matter presumably by different mechanisms. Resistance to desorption was generally highest among the NACs, and lowest among the nitramines, which include RDX and HMX. No single soil property appears to control the degree of resistance to desorption. The reversible / resistant model of Di Toro and Horzempa was applied successfully to the data with similar success, and enables an evaluation of both the aqueous and solids concentrations of explosives after multiple wetting events.University of Delaware, Department of Civil and Environmental EngineeringM.C.E